Multiple sources said Nagin has retained the services of Robert Jenkins. Those same sources said the former mayor has been asked by federal investigators to turn over certain financial and business documents by the end of the week.

When contacted by the I-Team, Jenkins declined comment.

In late 2010, Nagin's deputy mayor, Greg Meffert, pleaded guilty to charges that he accepted bribes while at City Hall. Meffert's sentencing has been delayed several times -- an indication that he may be cooperating with the U.S. Attorney's Office.

A city contractor, Aaron Bennett, has also pleaded guilty in connection with a bribery scheme.

Nagin has not been charged with any crimes and has repeatedly denied that he is the target of a federal probe, though reports earlier this year suggested that a formal investigation was under way.

Jenkins' client list includes former Jefferson Parish President Aaron Broussard, who is currently facing federal charges stemming from his term in office.

A Justice Department civil rights investigation has concluded that the Ferguson Police Department and the city's municipal court engaged in a "pattern and practice" of discrimination against African Americans.